What happened
Shortly after touchdown at Memphis, Tennessee, the flightcrew experienced a severe vibration within the cockpit. Believing the disturbance originated from the right main landing gear, the crew requested that maintenance personnel inspect the assembly. The inspection found no anomalies, and the flight continued to Pittsburgh, Pennsylvania.
Upon arrival in Pittsburgh, the aircraft landed normally. However, shortly after touchdown, the left main gear collapsed. Post-incident examination of the collapsed gear revealed that two spacers within the torque link assembly had been improperly installed.
The investigation
Further investigation determined that during the reinstallation of the torque links and shimmy damper at the previous maintenance check, the two spacers were placed in reverse of their normal positions. According to Fokker, this reversal created an undamped free play between the upper and lower torque link components. This mechanical defect resulted in oscillations within the lateral mode of the landing gear.
A review of USAir's Aircraft Maintenance Manual, which was supplied by Fokker, showed that the manual did not describe the two spacers with specific dimensions or descriptive verbiage. This lack of detail contributed to the error during reinstallation.